Eiger conqueror Sir Ranulph Fiennes has set himself a new challenge: the Bob Graham Round.

The Bob Graham is a punishing route over 42 Lakeland fells, covering around 63 miles, all to be completed in less than 24 hours. It involves about 26,000ft of ascent.

Blencathra, with Hall's Fell Ridge, on the Bob Graham Round 

Sir Ranulph, whose list of exploits included visiting both the North and South Pole by land, running seven marathons in seven days on different continents and sawing off the frostbitten finger ends of one hand in his garden shed, will attempt the circuit this summer.

He said he had the idea as an alternative to taking part in the Lowe Alpine Mountain Marathon. Sir Ran, cousin of film actor Ralph Fiennes, will start the run at 1am on 28 July from its official setting-off point, the Moot Hall in the centre of Keswick. The route includes Scafell Pike, Helvellyn and Skiddaw and is reckoned to be one of the best tests of fellrunning stamina in the country.

He will attempt the round in a clockwise direction, ascending Skiddaw first, with his team of pacers and support runners, which are permitted in the Bob Graham Round. He will need to maintain a speed of about 4.5km/hour to complete the distance in 24 hours.

The Bob Graham has amassed a plethora of myths and differing ‘facts’ since it was first achieved by the man it was named after, in June 1932. Wildly differing distances are quoted for the route, which is not a race, except against the clock, and which can be undertaken at any time by participants. Modern mapping analysis has given a distance of about 63 miles, somewhat less than the traditional 72 quoted for many years.

It is said that Mr Graham, who ran a Keswick guest house, did the original round in tennis shoes, shorts and a pyjama top! He made his first attempt the previous year, aiming for 41 peaks – one for each year of his age. Having failed, he added Great Calva, in the Back o’Skiddaw, the following year, making the 42 which most runners (or consistently fast walkers) now tackle.

Around 1,200 have achieved the feat, including record holder Billy Bland, who completed the round in a scorching 13h 54mins. Others have extended the route to include extra peaks. Mark Hartell holds the current record for the highest number of peaks in 24 hours with his 77, set in 1997.

63-year-old Sir Ranulph’s most recent adventure was the climb of the North Face of the Eiger, completed to raise money for Marie Curie Cancer Care.